SOIL-AQUIFER INTERACTIONS AND VADOSE ZONE MODELING: AN EXAMPLE FROM MARAIS POITEVIN (WESTERN FRANCE)

Abstract

Water flux in unsaturated zone is one of the most important phenomenon for determining the recharge characteristics of an aquifer. In-situ measurement and simulation models have been developed in recent years to characterize the recharge process in unsaturated zone. Recently, a mechanistic model named as "AgriFlux" have been adopted to specify the water fluxes in unsaturated zone. In this study, water flows in the unsaturated zone is investigated in order to understand a global interaction of soil-aquifer exchange system and to simulate the water flux leaching from unsaturated zone of soil and capacitance using AgriFlux model. Input parameters of the model were characterized by in-situ measurement and laboratory works. In-situ measurement were done by auger hole and Porchet test at 36 locations. Within laboratory tests, mineralogy of soil samples is characterized by X ray diffraction (XRD) and grain size distribution is determined on the undisturbed soil sampled from study area. The modelling results reveal that a percolated total water flow leaching through the unsaturated zone. The results were also compared with the observed ground water level fluctuations in the aquifer. Consequently, water flow quantification of a soil - aquifer system in Poitevin Marshland signpost the recharge characteristics of Bri Aquifer.